That means, with your current settings your head unit is putting out less than 1V through the preouts. As long as you keep those settings the "Low" setting is the correct setting to use on your amp, but the output will increase if you increase the volume, increase the bass, or turn loud on. So once you have the gain set leave the bass at 0, the "loud" off, and don't turn the volume above it's current level. If you are curious you can increase any of those settings and test the preouts again. That 5V spec in the manual is probably peak not RMS, the real RMS output is probably somewhere around 3-4V, but the only way you will ever see that is with everything maxed.ok i got .840 by touching the red inside and the black outside playin the test tone what does that mean